With this Funding Opportunity Announcement (FOA), the Department of Energy (DOE) SunShot Initiative is soliciting collaborative research teams to define and fabricate model systems that utilize a single p-n junction device structure and have the potential to approach Shockley-Queisser power conversion efficiency limits (for a chosen bandgap and absorber material). The emphasis of this FOA is assembling cohesive and highly diverse teams of experts within and outside the PV community who can achieve the goals of creating a model system concept and a subsequent device that can approach theoretical limits. DOE SunShot anticipates significant collaboration between experts in fundamental materials, characterization, device physics, ab-initio simulations, and PV device integration to adequately address these issues. The full Funding Opportunity Announcement (FOA) is posted on the EERE eXCHANGE website at https://eere-exchange.energy.gov. Applications must be submitted through the EERE eXCHANGE website to be considered for award. The applicant must first register and create an account on the EERE eXCHANGE website. A User Guide for the EERE eXCHANGE can be found on the EERE website http://eere.energy.gov/financing/exchangeExchange/Manuals.aspx after logging in to the system. Information on where to submit questions regarding the content of the announcement and where to submit questions regarding submission of applications is found in the full FOA posted on the EERE Exchange website.